期刊文献+
共找到41,114篇文章
< 1 2 250 >
每页显示 20 50 100
基于大模型的PDF文档转换实践
1
作者 李兴福 《科学与信息化》 2025年第15期35-38,共4页
PDF(便携式文档格式)是由Adobe公司在1993年推出的文件格式,其可以在任意设备或操作系统上都能保持一致的排版和格式,是在诸多领域广泛使用的标准化文档格式。然而,在众多特定应用场景下,用户对PDF文件的处理往往需要进行格式转换。随... PDF(便携式文档格式)是由Adobe公司在1993年推出的文件格式,其可以在任意设备或操作系统上都能保持一致的排版和格式,是在诸多领域广泛使用的标准化文档格式。然而,在众多特定应用场景下,用户对PDF文件的处理往往需要进行格式转换。随着人工智能技术的发展,利用大模型技术提供的先进文本处理能力,能够探求全新的PDF文档转换解决方案,推动相关技术与工具的发展变革,进而提升PDF转换的准确性与效率。 展开更多
关键词 大模型 pdf文档转换 OCR MinerU
在线阅读 下载PDF
PRO量表联合MRI-PDFF技术评估湿热证与非酒精性脂肪性肝炎的关联研究
2
作者 史会连 孙倩倩 +2 位作者 曹琛伟 陈权 乔飞 《时珍国医国药》 北大核心 2025年第22期4288-4293,共6页
目的探索中医湿热证与非酒精性脂肪性肝炎(NASH)严重程度的关系,研究中医证型的客观化。方法纳入902例NASH患者,依据报告结局量表(PRO)分为湿热证组(534例)和非湿热证组(368例)。所有患者均接受MRI-PDFF检测以评估肝脏脂肪含量,同时检... 目的探索中医湿热证与非酒精性脂肪性肝炎(NASH)严重程度的关系,研究中医证型的客观化。方法纳入902例NASH患者,依据报告结局量表(PRO)分为湿热证组(534例)和非湿热证组(368例)。所有患者均接受MRI-PDFF检测以评估肝脏脂肪含量,同时检测总胆固醇(TC)、甘油三酯(TG)、天门冬氨酸氨基转移酶(AST)、丙氨酸转氨酶(ALT)、谷氨酰转肽酶(GGT)等指标,比较两组间差异并分析相关性。结果湿热证组中重度脂肪肝比例显著高于非湿热证组(P<0.05),MRI-PDFF测得的肝脂含量、血脂和肝功能指标亦显著升高,呈递增趋势,差异均具有统计学意义。统计分析显示,湿热证与MRI-PDFF脂肪含量、血脂和肝功能指标呈正相关。结论中医湿热证与NASH病情严重程度密切相关,表现为肝脂肪含量和肝功能损伤明显加重,符合“湿热内蕴”理论。研究为中医证型的量化评估及NASH的早期干预提供了客观依据与新思路。 展开更多
关键词 非酒精脂肪性肝炎 报告结局量表 肝脏磁共振质子密度脂肪分数 湿热证
原文传递
基于CNN-BiLSTM-CBAM的多特征融合恶意PDF文档检测方法
3
作者 王友贺 孙奕 《信息网络安全》 北大核心 2025年第10期1579-1588,共10页
为应对现有恶意PDF文档检测方法忽视特征之间语义关系以及局限于单一类型的特征分析等问题,文章提出一种检测方案,将CNN-BiLSTM-CBAM的模型和多特征融合应用于恶意PDF文档检测中。该方法不仅融合了静态分析中提取的常规信息和结构信息,... 为应对现有恶意PDF文档检测方法忽视特征之间语义关系以及局限于单一类型的特征分析等问题,文章提出一种检测方案,将CNN-BiLSTM-CBAM的模型和多特征融合应用于恶意PDF文档检测中。该方法不仅融合了静态分析中提取的常规信息和结构信息,还结合了动态分析捕获的API序列信息,构建了一个全面多维的特征集。首先,该模型利用卷积神经网络提取特征集中的局部特征;然后,利用双向长短时记忆(BiLSTM)网络捕获特征间的依赖性和上下文语义关系特征,通过卷积块注意力模块(CBAM)为不同特征分配不同的权重,筛选出较具区分性的关键特征;最后,利用Softmax分类器计算检测结果。实验结果表明,与现有方法相比,该模型在准确率、召回率和F1分数等关键性能指标上均展现出显著优势,有效提升了恶意PDF文档的检测性能。 展开更多
关键词 恶意pdf文档检测 多特征融合 卷积块注意力模块 双向长短时记忆网络
在线阅读 下载PDF
Atmospheric reductive catalytic fractionation of lignocellulose integrated with one-pot catalytic conversion of carbohydrate yielding valuable lignin monomers and platform chemicals from corn straw 被引量:2
4
作者 Meng-Ying Liu Zhe-Hui Zhang +7 位作者 Xue-Qi Wang Qian Sun Chen Zhang Yu Li Zhuohua Sun Katalin Barta Feng Peng Tong-Qi Yuan 《Green Energy & Environment》 SCIE EI CAS 2025年第1期161-172,共12页
Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin f... Developing a cost-effective and environmentally friendly process for the production of valuable chemicals from abundant herbal biomass receives great attentions in recent years.Herein,taking advantage of the“lignin first”strategy,corn straw is converted to valuable chemicals including lignin monomers,furfural and 5-methoxymethylfurfural via a two steps process.The key of this research lies in the development of a green and low-cost catalytic process utilizing magnetic Raney Ni catalyst and high boiling point ethylene glycol.The utilization of neat ethylene glycol as the sole slovent under atmospheric conditions obviates the need for additional additives,thereby facilitating the entire process to be conducted in glass flasks and rendering it highly convenient for scaling up.In the initial step,depolymerization of corn straw lignin resulted in a monomer yield of 18.1 wt%.Subsequently,in a dimethyl carbonate system,the carbohydrate component underwent complete conversion in a one-pot process,yielding furfural and 5-methoxymethylfurfural as the primary products with an impressive yield of 47.7%. 展开更多
关键词 Atmospheric reductive catalytic fractionation Corn straw Ethylene glycol Raney Ni 5-Methoxymethylfurfural
在线阅读 下载PDF
一种融合多源信息的PDF地图扩展方法研究
5
作者 耿昊 李翔 +3 位作者 任芳 赵薇 宗磊 肖科宏 《测绘与空间地理信息》 2025年第8期30-33,37,共5页
针对目前PDF地图内容扩展方法不够明确、缺乏逻辑结构以及跨平台运行能力有限的问题,提出了一种基于Acrobat软件的融合多源信息的内容扩展方法。提出的方法在已有PDF地图和扩展内容的基础上,通过构建PDF地图和扩展文件的逻辑结构,进而... 针对目前PDF地图内容扩展方法不够明确、缺乏逻辑结构以及跨平台运行能力有限的问题,提出了一种基于Acrobat软件的融合多源信息的内容扩展方法。提出的方法在已有PDF地图和扩展内容的基础上,通过构建PDF地图和扩展文件的逻辑结构,进而构建文件存储目录,最终通过链接的方式形成扩展PDF地图。实验结果表明,该方法对于PDF地图内容扩展是可行和有效的,并具有较好的跨平台工作能力,能够在跨平台的场景下使用,例如面向不同电子设备用户群体分发电子地图。 展开更多
关键词 地图扩展 pdf地图 跨平台 多源信息
在线阅读 下载PDF
Impact of pitch fraction oxidation on the structure and sodium storage properties of derived carbon materials 被引量:1
6
作者 QI Su-xia YANG Tao +6 位作者 SONG Yan ZHAO Ning LIU Jun-qing TIAN Xiao-dong WU Jin-ru LI Hui LIU Zhan-jun 《新型炭材料(中英文)》 北大核心 2025年第2期421-439,共19页
Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation ac... Pitch produced by the lique-faction of coal was divided into two frac-tions:soluble in toluene(TS)and insol-uble in toluene but soluble in pyridine(TI-PS),and their differences in molecu-lar structure and oxidation activity were studied.Several different carbon materi-als were produced from them by oxida-tion in air(350℃,300 mL/min)fol-lowed by carbonization(1000℃ in Ar),and the effect of the cross-linked structure on their structure and sodium storage properties was investigated.The results showed that the two pitch fractions were obviously different after the air oxidation.The TS fraction with a low degree of condensation and abundant side chains had a stronger oxidation activity and thus introduced more cross-linked oxygen-containing functional groups C(O)―O which prevented carbon layer rearrangement during the carbonization.As a result,a disordered hard carbon with more defects was formed,which improved the electrochemical performance.Therefore,the carbon materials derived from TS(O-TS-1000)had an obvious disordered structure and a larger layer spacing,giving them better sodium storage perform-ance than those derived from the TI-PS fraction(O-TI-PS-1000).The specific capacity of O-TS-1000 was about 250 mAh/g at 20 mA/g,which was 1.67 times higher than that of O-TI-PS-1000(150 mAh/g). 展开更多
关键词 Pitch fractions Air oxidation Derived carbon materials Na^(+)storage
在线阅读 下载PDF
Local Rate of Convergence in the Functional Limit Theorem for Increments of a Fractional Brownian Motion 被引量:1
7
作者 LIU Yonghong DING Ding ZHOU Xia 《数学进展》 北大核心 2025年第1期197-211,共15页
In this paper,we present local functional law of the iterated logarithm for Cs?rg?-Révész type increments of fractional Brownian motion.The results obtained extend works of Gantert[Ann.Probab.,1993,21(2):104... In this paper,we present local functional law of the iterated logarithm for Cs?rg?-Révész type increments of fractional Brownian motion.The results obtained extend works of Gantert[Ann.Probab.,1993,21(2):1045-1049]and Monrad and Rootzén[Probab.Theory Related Fields,1995,101(2):173-192]. 展开更多
关键词 fractional Brownian motion INCREMENT local functional law of the iterated logarithm large deviation small deviation
原文传递
APPROXIMATE CONTROLLABILITY OF NONLINEAR EVOLUTION FRACTIONAL CONTROL SYSTEM WITH DELAY 被引量:1
8
作者 Kamla Kant MISHRA Shruti DUBEY 《Acta Mathematica Scientia》 2025年第2期553-568,共16页
This article studies the existence and uniqueness of the mild solution of a family of control systems with a delay that are governed by the nonlinear fractional evolution differential equations in Banach spaces.Moreov... This article studies the existence and uniqueness of the mild solution of a family of control systems with a delay that are governed by the nonlinear fractional evolution differential equations in Banach spaces.Moreover,we establish the controllability of the considered system.To do so,first,we investigate the approximate controllability of the corresponding linear system.Subsequently,we prove the nonlinear system is approximately controllable if the corresponding linear system is approximately controllable.To reach the conclusions,the theory of resolvent operators,the Banach contraction mapping principle,and fixed point theorems are used.While concluding,some examples are given to demonstrate the efficacy of the proposed results. 展开更多
关键词 nonlinear fractional differential equation Caputo fractional derivative mild solution existence and uniqueness theorems approximate controllability
在线阅读 下载PDF
Stromal vascular fraction: Mechanisms and application in reproductive disorders 被引量:1
9
作者 Zhi-Han Liu Qi-Qi Xie Jia-Lyu Huang 《World Journal of Stem Cells》 2025年第1期71-79,共9页
Stromal vascular fraction(SVF)is a complex mixture derived from adipose tissue,consisting of a variety of cells.Due to its potential for tissue repair,immunomod-ulation,and support of angiogenesis,SVF represents a pro... Stromal vascular fraction(SVF)is a complex mixture derived from adipose tissue,consisting of a variety of cells.Due to its potential for tissue repair,immunomod-ulation,and support of angiogenesis,SVF represents a promising frontier in regenerative medicine and offers potential therapy for a range of disease condi-tions.In this article,we delve into the mechanisms through which SVF exerts its effects and explore its potential applications in treating both male and female reproductive disorders,including erectile dysfunction,testicular injury,stress urinary incontinence and intrauterine adhesion. 展开更多
关键词 Stromal vascular fraction ANGIOGENESIS INFLAMMATION Regenerative medicine Reproductive disorders
暂未订购
Tourmaline and Mica Chemistry of the Wangxianling Granitoids,South China:Implications for Petrogenesis of Highly Fractionated Granite 被引量:1
10
作者 DUAN Xiaoxia WANG Ziyi +3 位作者 CHEN Bin ZHOU Lingli WANG Zhiqiang CHEN Yanjiao 《Acta Geologica Sinica(English Edition)》 2025年第3期789-805,共17页
Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline a... Both fractional crystallization and fluid-melt-crystal interaction are involved in the formation of highly fractionated granites.This paper assessed those two processes using geochemistry of muscovite and tourmaline and bulkrock chemistry of multi-phase Wangxianling granitoids,South China.Compositional variations suggest the coarse-grained muscovite granite is produced from fractional crystallization of the two-mica granite whereas the fine-grained muscovite granite represents a distinct magma pulse.Progressive fractionation of quartz,feldspar and biotite leads to elevated boron and aluminum content in melt which promoted muscovite and tourmaline to crystallize,which promotes two-mica granite evolving towards tourmaline-bearing muscovite granite.Fluid-melt-crystal interaction occurred at the magmatichydrothermal transitional stage and resulted in the textural and chemical zonings of tourmaline and muscovite in finegrained muscovite granite.The rims of both tourmaline and muscovite are characterized by the enrichment of fluid mobile elements such as Li,Mn,Cs and Zn and heavierδ^(11)B values of the tourmaline rims(-15.0‰to-13.6‰)compared to cores(-15.7‰to-14.3‰).Meanwhile,significant M-type REE tetrad effects(TE_(1,3)=1.07-1.18)and low K/Rb ratios(48-52)also correspond to fluid-melt-crystal interaction.This study shows zoned muscovite and tourmaline can be excellent tracers of fractional crystallization and late-stage fluid-melt-crystal interaction in highly evolved magmatic systems. 展开更多
关键词 TOURMALINE MUSCOVITE highly fractionated granite fluid-melt interaction South China
在线阅读 下载PDF
A multi-scale and multi-mechanism coupled model for carbon isotope fractionation of methane during shale gas production 被引量:1
11
作者 Jun Wang Fang-Wen Chen +4 位作者 Wen-Biao Li Shuang-Fang Lu Sheng-Xian Zhao Yong-Yang Liu Zi-Yi Wang 《Petroleum Science》 2025年第7期2719-2746,共28页
Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some sho... Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies. 展开更多
关键词 Shale gas Isotope fractionation MULTI-SCALE Production prediction Adsorbed/free gas ratio
原文传递
Large Deviations for Fractional Stochastic Heat Equation with Gaussian Noise Rough in Space
12
作者 WANG Zhi LIU Junfeng 《数学进展》 北大核心 2025年第6期1368-1392,共25页
In this paper we study the Freidlin-Wentzell's large deviation principle for the following nonlinear fractional stochastic heat equation driven by Gaussian noise∂/∂tu^(ε)=D_(δ)^(α)(t,x)+√εσ(u^(ε)(t,x))W(t,x... In this paper we study the Freidlin-Wentzell's large deviation principle for the following nonlinear fractional stochastic heat equation driven by Gaussian noise∂/∂tu^(ε)=D_(δ)^(α)(t,x)+√εσ(u^(ε)(t,x))W(t,x),(t,x)∈[0,T]×R,where D_(δ)^(α)is a nonlocal fractional differential operator and W is the Gaussian noise which is white in time and behaves as a fractional Brownian motion with Hurst index H satisfying 3-α/4<H<1/2,in the space variable.The weak convergence approach plays an important role. 展开更多
关键词 fractional stochastic heat equation fractional Brownian motion large deviation principle weak convergence
原文传递
PDF Search App助力临床药师实现快速文献检索
13
作者 耿江 张新军 《海峡药学》 2025年第3期123-126,共4页
临床药师需要经常性地检索阅读大量文献,传统单篇文献检索方法效率低下,难以满足实际需求。本文介绍了手机软件PDF Search对大量文献实现一次性检索并通过人工智能对相关性进行排序的方法,可大幅提高工作效率,以更好的为医生和患者提供... 临床药师需要经常性地检索阅读大量文献,传统单篇文献检索方法效率低下,难以满足实际需求。本文介绍了手机软件PDF Search对大量文献实现一次性检索并通过人工智能对相关性进行排序的方法,可大幅提高工作效率,以更好的为医生和患者提供专业化服务。 展开更多
关键词 pdf 人工智能 文献检索 临床药师
暂未订购
PDF文档双签双验的实现及其应用探索
14
作者 李文燕 殷豪 +2 位作者 谭敏清 方洪海 付祥 《中国标准化》 2025年第19期206-213,共8页
随着国家数字化进程的推进,数字签名作为提高各类电子文件有效性证明的信息技术手段,近几年越来越多地被社会广泛使用。国际上数字签名通常使用RSA算法,但根据我国商用密码应用相关政策要求,国内数字签名要求尽量使用国密算法,为了应对... 随着国家数字化进程的推进,数字签名作为提高各类电子文件有效性证明的信息技术手段,近几年越来越多地被社会广泛使用。国际上数字签名通常使用RSA算法,但根据我国商用密码应用相关政策要求,国内数字签名要求尽量使用国密算法,为了应对电子检验检测报告需要同时在国内外使用的特殊场景,研究基于RSA及SM2加密算法对PDF文档进行双签双验技术,并在认证认可检验检测电子证书在线验证平台中进行应用实践,不仅增加了数字签名认证认可检验检测电子证书(报告)国内外应用的便利性,而且大大提升了其准确性、真实性和不可篡改性。 展开更多
关键词 pdf 双签双验 电子证书 数字签名 RSA SM2
在线阅读 下载PDF
On the Relative Growth Rate of the Digits in Sylvester Continued Fraction Expansions
15
作者 LV Meiying RAO Guilin 《应用数学》 北大核心 2025年第2期468-476,共9页
For the Sylvester continued fraction expansions of real numbers,FAN et al.(2007)proved that,for almost all real numbers,the nth partial quotient grows exponentially with respect to the product of the first n-1 partial... For the Sylvester continued fraction expansions of real numbers,FAN et al.(2007)proved that,for almost all real numbers,the nth partial quotient grows exponentially with respect to the product of the first n-1 partial quotients.In this paper,we establish the Hausdorff dimension of the exceptional set where the growth rate is a general function. 展开更多
关键词 Sylvester continued fraction expansions Growth rate Hausdorff dimension
在线阅读 下载PDF
Least Energy Solutions for the Fractional Schrodinger–Poisson System with General Potential and Nonlinearity
16
作者 ZHU Shaojuan HUANG Xianjiu 《数学进展》 北大核心 2025年第5期1031-1058,共28页
In this paper,we study the existence of least energy solutions for the following nonlinear fractional Schrodinger–Poisson system{(−∆)^(s)u+V(x)u+φu=f(u)in R^(3),(−∆)^(t)φ=u^(2)in R^(3),where s∈(3/4,1),t∈(0,1).Und... In this paper,we study the existence of least energy solutions for the following nonlinear fractional Schrodinger–Poisson system{(−∆)^(s)u+V(x)u+φu=f(u)in R^(3),(−∆)^(t)φ=u^(2)in R^(3),where s∈(3/4,1),t∈(0,1).Under some assumptions on V(x)and f,using Nehari–Pohozaev identity and the arguments of Brezis–Nirenberg,the monotonic trick and global compactness lemma,we prove the existence of a nontrivial least energy solution. 展开更多
关键词 fractional Schrodinger-Poisson system variational method Nehari-Pohozaev identity least energy solution
原文传递
快速处理PDF地图注记与符号压盖关系的方法
17
作者 汶建龙 刘静祯 楼乐乐 《地理空间信息》 2025年第4期119-122,共4页
地形图是经济建设、国防建设和科学研究中不可缺少的工具,目前发挥着重要作用。地图上符号间压盖关系不仅反映现实世界中地物间的空间关系,而且直接影响地图的视觉表达效果,必须按制图规范正确处理。但地形图符号间压盖关系处理起来非... 地形图是经济建设、国防建设和科学研究中不可缺少的工具,目前发挥着重要作用。地图上符号间压盖关系不仅反映现实世界中地物间的空间关系,而且直接影响地图的视觉表达效果,必须按制图规范正确处理。但地形图符号间压盖关系处理起来非常复杂,始终难以突破手工编辑作业的瓶颈。比如当注记与要素符号相交时,同色要素符号一般需要间断表示,而其他非同色要素符号又不能受影响。目前这类工作往往需要结合制图经验,靠人工交互手工处理来完成,工作量必然非常繁重。针对当前地形图注记与同色符号压盖关系处理依然摆脱不了大量人工作业的现实问题,利用PDF文档同时具备专色和叠印的特性,提出了一种利用专色叠印蒙片自动快速处理PDF地图注记与同色符号压盖关系的方法。从实验效果看,该方法不仅能够完全解决注记与同色要素符号压盖关系问题,而且在很大程度上提高了工作效率,同时也减少了作业人员对制图知识和技术经验的过度依赖,具有很好的推广应用价值。 展开更多
关键词 地形图 pdf地图 注记 要素符号 压盖关系 专色 叠印 蒙片
在线阅读 下载PDF
Independent and interactive effects of N and P additions on foliar P fractions in evergreen forests of southern China 被引量:1
18
作者 Qingquan Meng Zhijuan Shi +3 位作者 Zhengbing Yan Hans Lambers Yan Luo Wenxuan Han 《Forest Ecosystems》 2025年第1期66-73,共8页
Fertilization or atmospheric deposition of nitrogen(N)and phosphorus(P)to terrestrial ecosystems can alter soil N(P)availability and the nature of nutrient limitation for plant growth.Changing the allocation of leaf P... Fertilization or atmospheric deposition of nitrogen(N)and phosphorus(P)to terrestrial ecosystems can alter soil N(P)availability and the nature of nutrient limitation for plant growth.Changing the allocation of leaf P fractions is potentially an adaptive strategy for plants to cope with soil N(P)availability and nutrient-limiting conditions.However,the impact of the interactions between imbalanced anthropogenic N and P inputs on the concentrations and allocation proportions of leaf P fractions in forest woody plants remains elusive.We conducted a metaanalysis of data about the concentrations and allocation proportions of leaf P fractions,specifically associated with individual and combined additions of N and P in evergreen forests,the dominant vegetation type in southern China where the primary productivity is usually considered limited by P.This assessment allowed us to quantitatively evaluate the effects of N and P additions alone and interactively on leaf P allocation and use strategies.Nitrogen addition(exacerbating P limitation)reduced the concentrations of leaf total P and different leaf P fractions.Nitrogen addition reduced the allocation to leaf metabolic P but increased the allocation to other fractions,while P addition showed opposite trends.The simultaneous additions of N and P showed an antagonistic(mutual suppression)effect on the concentrations of leaf P fractions,but an additive(summary)effect on the allocation proportions of leaf P fractions.These results highlight the importance of strategies of leaf P fraction allocation in forest plants under changes in environmental nutrient availability.Importantly,our study identified critical interactions associated with combined N and P inputs that affect leaf P fractions,thus aiding in predicting plant acclimation strategies in the context of intensifying and imbalanced anthropogenic nutrient inputs. 展开更多
关键词 Anthropogenic nutrient inputs Individual and combined effects Interactive effects Leaf phosphorus fractions Nitrogen and phosphorus additions Nutrient-utilization strategies Woody plants
在线阅读 下载PDF
A composite controller for reactor core combining artificial neural network and fractional-order PID controller
19
作者 WANG Zhe-Zheng ZHANG Xiao DENG Ke 《四川大学学报(自然科学版)》 北大核心 2025年第4期1015-1024,共10页
Core power is a key parameter of nuclear reactor.Traditionally,the proportional-integralderivative(PID)controllers are used to control the core power.Fractional-order PID(FOPID)controller represents the cutting edge i... Core power is a key parameter of nuclear reactor.Traditionally,the proportional-integralderivative(PID)controllers are used to control the core power.Fractional-order PID(FOPID)controller represents the cutting edge in core power control research.In comparing with the integer-order models,fractional-order models describe the variation of core power more accurately,thus provide a comprehensive and realistic depiction for the power and state changes of reactor core.However,current fractional-order controllers cannot adjust their parameters dynamically to response the environmental changes or demands.In this paper,we aim at the stable control and dynamic responsiveness of core power.Based on the strong selflearning ability of artificial neural network(ANN),we propose a composite controller combining the ANN and FOPID controller.The FOPID controller is firstly designed and a back propagation neural network(BPNN)is then utilized to optimize the parameters of FOPID.It is shown by simulation that the composite controller enables the real-time parameter tuning via ANN and retains the advantage of FOPID controller. 展开更多
关键词 Nuclear reactor Core power fractional PID controller Artificial neural network
在线阅读 下载PDF
Transportation Cost-information Inequalities for Stochastic Heat Equations Driven by Fractional Noise
20
作者 ZHANG Bin YAO Zhigang LIU Junfeng 《数学进展》 北大核心 2025年第1期212-224,共13页
In this paper,we prove the transportation cost-information inequalities on the space of continuous paths with respect to the L~2-metric and the uniform metric for the law of the mild solution to the stochastic heat eq... In this paper,we prove the transportation cost-information inequalities on the space of continuous paths with respect to the L~2-metric and the uniform metric for the law of the mild solution to the stochastic heat equation defined on[0,T]×[0,1]driven by double-parameter fractional noise. 展开更多
关键词 transportation cost-information inequality stochastic heat equation fractional noise
原文传递
上一页 1 2 250 下一页 到第
使用帮助 返回顶部